Just a thought, but...
Unless you NEED to be more accurate, just buy the cheapest "name brand" ammo you can find and concentrate on shooting technique. I used to buy blocks of remmington thunderbolt .22, and it shot just fine in my 10-22, good enough that I could see the results of good or bad technique in my groupings.
I also found that lightweight or high speed ammo was rarely more accurate than even the thunderbolt stuff, which is derided as "bad" ammo by some people.
My best advice is to try various inexpensive types before you try any sort of premium or specialty ammo like subsonic or ultra high-speed. If you can't find decent results with the cheap stuff then try various extreme stuff like lightweight/fast, lightweight slow, heavyweight, etc. But if you can't find a decent ammo that doesn't cost a lot, then chances are you are up against either a technique problem or a basic limitation of the gun.
My mini-14 is sort of like that... The best ammo I found for it is anything with heavyweight bullets, the heavier the better. But no matter what ammo I use and no matter who is shooting it (taking technique out of the equation), it still shoots no better than 3 inch groups at 100 yards, so I've found the limits of the gun. If you can't find a good ammo and everyone gets the same results, then you may be at the limits of that gun.
It is disappointing to find that you are a more accurate shooter than your gun is capable of delivering, but throwing money at a gun that is already more accurate than you are is likewise frustrating.